This invention relates to a cutting tool for a mining machine for cutting a variety of soft materials such as coal.
Cutting tools of this type comprise a holding lug and an insert secured in a bore or socket in the lug. A plurality of the cutting tools are positioned on a working surface, for example on the surface of a drum, and moved in a cutting direction against the face of the material to be cut.
The insert which is secured in the socket or bore in the lug will preferably contain abrasive compact as the cutting edge. In one known embodiment, that described in U.S. Pat. No. 4,655,508, the insert comprises an elongate cemented carbide stud, a recess formed in one end of the stud, the stud having surfaces sloping away from the recess to provide a shoulder which completely surrounds the recess and a complete abrasive compact or an abrasive compact located in the recess and bonded to the stud and presenting an abrasive compact cutting edge or surface. When the insert is located in the socket in the lug the shoulder provides a protective surface of the area of the lug around the socket acting to deflect material being cut away from the lug. The life of the lug which is made of steel, is thus prolonged. While an insert of the type described above has been found to work well and achieves its objective for soft coals, problems do arise when the insert is used for cutting harder coals. The extensive surface area of the shoulder places great mechanical stress on the insert and fracture of the holding lug or dislodgement of the insert itself from the lug can occur.
U.S. Pat. No. 4,678,237 describes a stud for use in a mining pick which has a tip consisting of polycrystalline diamond composite and a body having a carrying surface on which the tip is mounted, the carrying surface being inclined to the axis of the body at an angle between 45.degree. and 65.degree.. The stud is received within a pocket in the head of a mining pick, the axis of the pick and the axis of the stud being substantially coincident.